The goal of this project is to develop a personal, self-contained circadian light and activity measurement device to correct sleep disorders in young adults. Integrated into the envisioned system will be two-way communication capabilities so that real-time light and activity data can be acquired by remote computer for immediate processing and then for generation of a light (and dark) exposure recommendation for any desired circadian phase entrainment desired by the young adult. Commonly adolescents and young adults experience age-dependent delayed sleep phase with respect to socially acceptable activity/rest periods. This lack of entrainment to socially acceptable activity/rest periods can lead to reduced sleep duration and efficiency which in turn can lead to a number of symptoms of psychosocial stress. A personal device that can accurately measure light/dark exposures as well as periods of activity/rest is envisioned for correcting circadian entrainment problems in young adults. A regression model for predicting circadian entrainment from light and activity data will be developed based upon a controlled light intervention study. To augment the model, changes in gene expression following the controlled light intervention will be assessed as well as changes in gene expression following the controlled light intervention. Based upon the regression model and the personal light and activity data, it will be possible to prescribe specific times and amounts of light (and dark) for a person to experience such that she/he can entrain to any desired circadian phase. Thus, a powerful personal measurement and communication device will be developed for alleviating symptoms of psychosocial stress caused by sleep disorders in young adults. The sleep laboratory at Brown University will be the site of the activity/rest calibration studies. In addition to the light and activity data needed for refinement of the model to predict circadian phase, measures related to an individual's rest and activity, such as BMI and sleep duration, will be included in a regression model to better predict circadian phase shifting following a controlled light intervention. Yale University will measure the impact of light exposure on circadian gene expression. The personal device proposed here can be used for any applications associated with circadian sleep disorders, such as jet lag and shift work. [unreadable] [unreadable] [unreadable]